The default rate on debt issued by U.S. companies with the lowest credit ratings was 2.8% in October, up dramatically from the 2% at the start of the year, says Standard & Poor's. During the year, 42 U.S. companies defaulted.

While defaults have risen, they haven't skyrocketed as much as some feared they would given the lackluster growth of the economy.

A big reason why companies aren't being backed into a wall is because investors have been buying up corporate bonds, pushing interest rates down.

Investors are willing to lend money to companies with the lowest credit ratings for just 5.92 percentage points over Treasuries with comparable terms.

That's a very affordable rate for many companies to deal with, even when the economy isn't rip roaring. And because rates are so low, S&P says the level of financial stress on companies fell more than 10% in the summer.

There's so much demand for corporate debt, companies are selling more.

Corporate bond issuance has jumped in 2012, with 835 U.S. companies issuing debt, up more than 13% from the full year of 2011, S&P says.